1. Field of the Invention
The present invention relates to agricultural implements, and, more particularly, to lift systems for such implements.
2. Description of the Related Art
Farmers utilize a wide variety of tillage implements to prepare soil for planting. Some such implements include two or more sections coupled together to perform multiple functions as they are pulled through fields by a tractor. For example, a field cultivator is capable of simultaneously tilling soil and leveling the tilled soil in preparation for planting. A field cultivator has a frame that carries a number of cultivator shanks with shovels at their lower ends for tilling the soil. The field cultivator converts compacted soil into a level seedbed with a consistent depth for providing excellent conditions for planting of a crop. Grass or residual crop material disposed on top of the soil is also worked into the seedbed so that it does not interfere with a seeding implement subsequently passing through the seedbed.
As tillage implements become wider and wider over time, it becomes more difficult to keep the transport size of the implement within manageable limits. It also becomes more difficult to convert the tillage implement from an operating mode to a transport mode, or vice versa, without requiring too much time and difficulty on the part of the operator. It is desirable for the tillage implement to be converted from one mode to the other while the operator remains within the operator cab, through the use of hydraulics or other actuators. It is also desirable for the tillage implement to remain within certain geometric constraints so that it is not necessary to use a separate “escort vehicle” or the like when traveling on public roads.
Tillage implements of this type have a plurality of wheels supporting the implement and fashioned to form a lift system which positions the implement at variable positions above the soil. When the implement is in the field, the lift system positions the implement either in a field transport position where any ground engaging tools are just above the soil and an operational position in which the tools penetrate the soil for tillage and other operations. When the implement is to be transported between fields, the lift system places the implement in a transport position in which the tools are well clear of the soil. The wheels that are part of the lift system must have several requirements. When the implement is in the field, it is extended to its full lateral position and in this position the wheels must be fixed to enable the laterally extending implement to track properly through the field. On the other hand, during the transport position in which some sections of the implement are folded, the wheels must be able to castor so that tracking down a road between fields is possible.
What is needed in the art therefore, is a simplified and effective system for locking the lift system wheels in the field and allowing them to castor during transport.